Balloon mold



Feb. 8, 1949. HABlB ET AL I 2,461,270

' BALLOON MOLD Filed Feb. 19, 1946 Emile E. "Hob/b 8 8H David 6. Green/IW301i. C 13m Gttorneg.

Ihwentorsi Patented Feb. 8, 1949 BALLOON MOLD Emile E. Habib, Arlington,and David G. Greenlie, Wayland, Mass., assignors: to Dewey and AlmyChemical Company, North Cambridge, Mass, a corporation of MassachusettsApplication February 19, 1946, Serial No. 648,674

3 Claims.

This invention relates to the manufacture of hollow inflatable objectsand is particularly adapted to the manufacture of meteorologicalballoons of medium and large size. These balloons must fit standardizedinflation equipment. It is essential, therefor, that the balloons havestandardized neck diameters to fit the inflating apparatus which existsin the field.

Recently, there has been a need for meteorological balloons havinginflated diameters at 760 mm., of approximately 8 feet and even larger.If balloons of such size are manufactured by gel inflation techniques,e. g., by that process disclosed in the patent to Habib and Gott No.2,378,702, dated June 19, 1945, and if the neck diameter of the largermould required to make these large balloons is held to the size alreadyaccepted as standard for the smaller ones, it will be found that thenecks of the large balloons are weakly attached to the balloon envelopeand tear out of the envelope when any heavy wind strain is imposed.

The present invention permits the manufacture of meteorological balloonshaving necks which are so securely attached to the balloon envelope thatthey will withstand any strain that the balloon envelope proper willtake. In addition, the invention makes it possible to make a balloonhaving a substantial body diameter yet possess a much smaller diameterneck than any which has heretofore been possible.

We have discovered that if a mold is provided which will form anintermediate section of gel between the body and the neck whichpossesses a considerably greater diameter than the neck itself, thatwhen the gel is inflated, the intermediate portion will be drawn intothe lower hemisphere of the balloon envelope. But this new portion ofthe hemisphere will taper from the full thickness of the neck where itjoins the neck to its juncture with the envelope where it has only thethickness of the envelope.

Additionally, the diameter of this tapered zone is directly related tothe original diameter and length of the intermediate section and to thedegree of inflation.

It is customary in the manufacture of meteorological balloons to formthe balloon envelope by dipping a fluted mold into an aqueous dispersionof rubber. A fluted mold is much more compact and weighs much less thana non-fluted spherical mold, yet the lunettes of gel expand verysmoothly into a, spherical shape when the gel is enlarged in area. Byfar the simplest method of expanding a. gel is to blow air into thehollow gelgform, but other methods of gel expansion such as liquidpressure, stretching by pulling, or exhausting the air in thesurrounding space are not excluded.

The invention may be more readily understood by reference to thedrawings, in which Figure 1 is an elevation of the preferred form of thedipping mold;

ure 2 is a transverse section taken on the line 2-2 of Figure 1;

Figure 3 is a sectional elevation of a portion of an inflated balloonenvelope; and I Figure 4 is an elevation of a modified form of balloonmold.

Referring to Figure 1, the mold I0 is preferably formed with a shankportion H, and a body or flute portion l2. Intermediate the flue portionl2 and the shank H, the flutes lose their lunette form and extendparallel tothe axis of the shank as shown at l3.

When following any accepted gel inflation technique, the mold I8 isdipped into an aqueous dispersion of rubber up to a line on the shank Hwhich is indicated by the reference numeral I 4. When a deposit ofsufficient thickness has been formed, the mold is withdrawn and therubber deposit, still in a, plastic, gel stage, is stripped from themold. The end of the neck portion 6 of the deposit isfitted over aninflation nozzle N, then a clamp or tape-tie is tied about the neck atthe point [5. The gel is then inflated.

We have found that if the balloon is to be approximately spherical, theaxial perimeter of the flutes including the portions l2 and l 3 mustequal approximately the transverse maximum peri-- meter, 1. e'., theperimeter of the section 2--2. When other shapes are required, thisratio of perimeters' is no longer necessary.

As Figure 3 shows, the neck 5 of the gel remains the same diameter, asthe inflating nozzle but that portion 16 of the deposit which was formedon the parallel section l3 of the flutes, flares out into the l6 joinsthe body of the envelope, as indicated at IT, and thickest where theportion [6 Joins the neck, as indicated at l8.

As an example, if an army standard meteorological balloon is made on afluted mold having a maximum perimeter of 34" around all flutes, aperimeter of 7.1" around the shank flutes, a shank 1.063" in diameter,and if the length of the fluted section parallel to the shank I3 is 3",then this balloon gel when inflated to 44" in diameter will have athickness-tapered, reinforced zone surrounding the neck about 11" indiameter. The neck will be 1 in diameter. Obviously, the

size of this zone of reinforcement for the neck is determined by and maybe varied by changes in the following factors:

(a) The length of the parallel section I3 of the flutes of the mold (b)By the perimeter of the same section, and

(c) By the amount of the gel extension introduced by the gel-inflationstep.

In order for the reinforcing section to taper smoothly from the balloonbody to the neck, it is preferred to hold the ratio of the perimeter ofthe gel formed on the mold section 13 to, the maximum perimeter of thegel formed on the flutes i 2 to approximately 6:1. or less. If thediiierence in perimeters is much greater than 6: 1, then for any giveninflating pressure, the lunette sections 12 will expand practically tothe exclusion of the reinforcing section 13. In this case, a thinningand weakening of the gel at the point ll sometimes occurs. When theperimeter ratios are held approximately to the recommended limits, theintermediate section 13 is drawn smoothly into the body of the balloon.

Figure 4 illustrates the shape of mold found useful when the balloonenvelope must be large and the neck quite small. The first step I9 ofthe reinforcing zone has a perimeter which is one sixth or a largerfraction of the maximum perimeter of the body portionof the gel. secondstep 20 has a perimeter which in turn is one sixth or a larger fractionof the perimeter of the gel formed on step i9. Obviously, as many stepsas are necessary may be used to produce a smooth, tapered reinforcingflange between the body of the balloon and the neck. Two steps, however,will produce a finished balloon having an envelope diameter of 12 feetand a neck di ameter of 2 inches.

The word perimeter as applied to fluted molds means the unfolded ordeveloped distance progressively from root to apex of the convolutionsaround the form or the gel deposited upon the forming flutes as thesense requires.

The word rubber has been used to include natural rubber having theproper characteristics, for example, see Patent No. 2,378,700,chlorobutadiene 1.3 and the various artificial elastomers the gels ofwhich possess suflicient strength to permit the requisite expansion.

For convenience in the specification and claims we have used the wordgel to denote the undried, irreversible coagulum deposited upon a moldby the action of a coagulant while that deposit contains a majorproportion of its original aqueous constituent uniformly distributed inthe coagulated rubber network.

Although the invention has been described as applied to meteorologicalballoons and fluted molds, it is useful in the formation ofany necked,

The

4 hollow body and with molds of any construction. For example, sphericalmolds may be built according to this invention with a cylindricalintermediate flange-forming section interposed between the sphericalbody and the shank of the mold.

Balloons produced by this invention have successfully met therequirements for small necks, large envelopes, and possess suflicientstrength in the neck reinforcement to suspend meteorological apparatusin all normal weather conditions.

We claim:

1. A balloon mold having neck-forming shank and a fluted body-formingportion and a fluted portion intermediate between said body portion andsaid shank having a perimeter smaller than but at least one-sixth of themaximum perimeter of said body portion, said neck-forming shank having aperimeter smaller than but at least onesixth of the perimeter of saidintermediate portion.

2. A mold for forming spherical meteorological balloons including ashank and flutes extending from said shank and having the outer marginof said flutes extending for a limited distance parallel to the axis ofsaid shank and then assuming a lunette form of larger perimeter than theparallel portion the combined length of the parallel and lunetteportions of the flutes being approximately equal to the maximumperimeter of the flutes normal to the axis of the mold.

8. A mold according to claim 1 having a plurality of fluted portionsintermediate between said body-forming portion and said shank andarranged in stepped relation with the perimeters of the respectivefluted portions increasing from the shank toward the body-formingportion, each of said fluted portions having a perimeter smaller than,but at least one-sixth of the maximum perimeter of the next adjacentlarger portion, said neck-forming shank having a perimeter smaller thanthat of the intermediate fluted portions but at least one-sixth of theperimeter of the-adjacent intermediate portion.

EMILE E. HABIB; DAVID G. GREENLIE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Habib et a1 June 19, 1945

